4. 8 - 2x - x^2 = (x-2)(x+4)
5. y^2 - (y^2 - 2y + 1) = 2y - 1
6. 4xy - (x^2 + 2xy + y^2) = 2xy - x^2 - y^2
7. 15w - 36 + w^2 - 12w + 36 = w^2 + 3w = w×(w + 3)
8. 1 + 3p^2 - 4p^2 + 4p - 1 = 4p - p^2 = p×(4-p)
9. 4 - 12a + 9a^2 - 64a^4 + 32a^2 - 4 = 41a^2 - 64a^4 - 12a
10. a^2 - 2ab + b^2 + 2ab - 2a^2 = b^2 - a^2 = (b-a)(b+a)